Gas Sensor Based on Silicon Nitride Integrated Long Period Grating.

In this paper, we demonstrate the potential of silicon nitride integrated long period grating (LPG) for gas sensing applications. The proposed LPG relies on the coupling of the single core mode propagating in the silicon nitride layer to cladding mode(s) by using a periodic sinusoidal width-modulation of the LPG core as pattern. This LPG is then used as CO2 sensor. Here, as a proof of concept, the cladding layer is itself a porous medium functionalized to CO2 using Polyhexamethylene Biguanide polymer. Preliminary experimental results show a constant sensitivity of 6.3 fm/ppm over CO2 concentration ranging from [0-20%].